Different cables having different conductor areas but same current rating?

[Jodes]

Why would two cables have the same current rating, but different conductor surface area?

I'm looking at double insulated thin wall 2-core 25A multistrand cable.

In one case the conductor area is 2mm^2, in the other it's 8.4mm^2.

Is this a mistake by a supplier? Or maybe one cable has better heat dissipation or something?

Cheers

 

[Marvo]

It could be down to one cable having better heat dissipation characteristics but more likely the insulation material on one has a higher temperature capability. Also finer stranded wire tends to have a lower impedance at the same cross-sectional surface area due to skin effect.

**edit**
Just noticed you're a DIY'er but this sounds more like a trainee/apprentice type question........

 

[Engineer54]

It's down to the skin effect, fine multi stranded cables have an overall larger surface area and thus a lower impedance...

 

[Marvo]

Why would two cables have the same current rating, but different conductor surface area?

I'm looking at double insulated thin wall 2-core 25A multistrand cable.

In one case the conductor area is 2mm^2, in the other it's 8.4mm^2.

Is this a mistake by a supplier? Or maybe one cable has better heat dissipation or something?

Cheers

I've never heard of an 8.4mm sq wire size.

 

[Jodes]

I thought skin effect only applied to AC?

The 8.4mm2 was 28 strands of 0.3mm2

The other cable does not have the number of strands specified

Edit: There's no option for "Smart-arse Know-it-all", otherwise I'd have chosen that.

 

[Marvo]

I thought skin effect only applied to AC?

Skin effect applies to modulated direct currents such as PWM but not to pure DC such as a battery current.

The 8.4mm2 was 28 strands of 0.3mm2

A 28/0.3 wire isn't a standard electrical LV power wire, it's what we call ELV panel flex and it's sometimes used in automotive wiring but it might go under a different name in the UK.

The 28 refers to the number of strands but the 0.3 refers to the diameter of the strands, not the cross-sectional area of them. A 28/0.3 wire is nowhere near being a 8.4mm² equivalent, it's pretty close to being a 2mm² conductor which would normally be capable of somewhere around 20Amps current handling at a push.

Edit: There's no option for "Smart-arse Know-it-all", otherwise I'd have chosen that.

If you were a student or apprentice I was going to suggest you apply for access to our trainee area.

 

[Engineer54]

To be totally honest i didn't even realise i was on the Auto Electrician forum, i rarely if ever even look in that forum, (i entered the forum via the ''new posts'' listings) So completely unaware we were talking about DC voltage, especially as there was no reference in the OP's thread to auto wiring!!

 

[Marvo]

To be totally honest i didn't even realise i was on the Auto Electrician forum, i rarely if ever even look in that forum, (i entered the forum via the ''new posts'' listings) So completely unaware we were talking about DC voltage, especially as there was no reference in the OP's thread to auto wiring!!

Don't worry, I was also a bit slow off the mark and didn't realise it might be automotive wiring until the last post I made.